Optical component

ABSTRACT

A passive optical component directs first electromagnetic radiation incident on the component in a first direction and second electromagnetic radiation incident on the component in a second direction to a mutual direction. The optical component comprises an interacting surface which is arranged to interact with said first and second electromagnetic radiation. The interacting surface comprises first portions, each having a surface extending in a third direction, which is essentially perpendicular to the mutual direction, and second portions, each having a surface extending in a fourth direction. The optical component reflects essentially all the first electromagnetic radiation and transmits at least a significant portion of the second electromagnetic radiation for directing the first and the second electromagnetic radiation to a mutual direction. An optical system and a method using the passive optical component are also shown.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a passive optical component fordirecting first electromagnetic radiation incident on the component in afirst direction and second electromagnetic radiation incident on thecomponent in a second direction to a mutual direction. The presentinvention also relates to an optical system and a method using such apassive optical component.

BACKGROUND OF THE INVENTION

In several applications there is a need for emitting electromagneticradiation containing two different wavelengths towards a specific point.Such an application may be a spectrophotometric analysis, where a sampleis irradiated with the two different wavelengths and the interaction ofthe electromagnetic radiation and the sample is registered. The twodifferent wavelengths are needed, since properties of the sample may bedetermined by establishing a ratio between the interactions of thesample with the different wavelengths.

There are a number of solutions to the need for emitting electromagneticradiation containing two wavelengths towards a sample. According to afirst solution, the sample is first irradiated by radiation of a firstwavelength and then irradiated by radiation of a second wavelength. Thismay be accomplished by for example selectively activating a mirror foroptionally directing the first radiation or the second radiation towardsthe sample to be irradiated. However, this requires a mechanicallymoveable component, which sets high demands on the stability of thesetup and also makes the setup complex.

According to a second solution, the sample is irradiated by differentwavelengths in different positions. However, then the radiation ofdifferent wavelengths will not interact with the same parts of thesample. Therefore, differing properties of the different positions ofthe sample, such as differing thickness of the sample, could affect theresult of the analysis.

According to a third solution, the sample may be irradiated by a sourcewhich emits a wide spectrum of wavelengths. However, if two specificwavelengths are needed, there may not be any source that emits these twowavelengths.

According to a fourth solution, a beam splitter may be used. Radiationincident on a beam splitter will be partly reflected and partlytransmitted. Radiation of a first wavelength may then incide on one sideof the beam splitter and radiation of a second wavelength may incide onthe other side of the beam splitter. Part of the radiation of the firstwavelength will then be transmitted through the beam splitter and willbe collimated with the part of the radiation of the second wavelengththat is reflected by the beam splitter. However, only 50% of thecombined radiation intensity of the wavelengths may be used in themeasurement, since the rest of the radiation is directed by the beamsplitter-away from the sample position.

According to a fifth solution, an active component may be used. Theactive component acts in a similar manner as the beam splitter. However,by applying a voltage over the active component, it may reflect 100% ofthe radiation incident on one side. When the voltage is turned off, theactive component transmits 50% of the radiation incident on the otherside. The active component requires an extra electric circuit for itsactivation. This makes the design of an optical setup using the activecomponent more complex. Further, a measurement requires switching on andoff the voltage applied to the active component.

SUMMARY OF THE INVENTION

It is an object of the invention to provide an optical component, whichmay overcome the above-identified problems and which provides betteroptical characteristics for radiation from different directions withoutthe need of any active manipulation of the optical setup.

The object of the invention is achieved by a passive optical componentaccording to claim 1. The object of the invention is also achieved by anoptical system according to claim 11 and a method according to claim 16,wherein the inventive idea is used for spectrophotometric analysis.

According to the invention, a passive optical component is provided fordirecting first electromagnetic radiation incident on the component in afirst direction and second electromagnetic radiation incident on thecomponent in a second direction to a mutual direction. The opticalcomponent reflects essentially all the first electromagnetic radiationand transmits at least a significant portion of the secondelectromagnetic radiation for directing the first and the secondelectromagnetic radiation to a mutual direction.

In the context of this application, the term “passive optical component”should be interpreted as any optical component that has constant opticalcharacteristics, i.e. the optical component should not need any outerinfluence in order to present its optical characteristics. Further, asused herein the phrase “reflect essentially all radiation” means thatmost of the radiation is reflected but losses due to e.g. surfacereflection or absorption may occur. Also, the phrase “transmit at leasta significant portion of radiation” should be interpreted as that asubstantial amount of the radiation is transmitted, i.e. the portionneed not be 50% but should be large enough to be clearly detectable.

The passive optical component according to the invention allows moreradiation to be directed towards a specific point than is allowed byconventional devices. Further, the passive optical component providesthe funcionality through a small size component, which involves nomoveable parts, and therefore is robust.

Preferably, there is provided a passive optical component comprising aninteracting surface which is arranged to interact with electromagneticradiation. The interacting surface has first portions, each having asurface extending in a third direction and second portions, each havinga surface extending in a fourth direction. The first and second portionsmay be so arranged that essentially all radiation incident on one sideof the interacting surface from the first direction and a significantportion of radiation incident on the other side of the interactingsurface from the second direction will be directed by the interactingsurface to a mutual direction.

By intelligent arrangement of the first portions relative the firstdirection of incident radiation, the interacting surface seen from thefirst direction may appear to be consisting only of the second portions.This may be accomplished by arranging the first portions such that thesurfaces of the first portions extend in a direction parallel to thefirst direction of incident radiation. Thus, all the radiation incidentfrom the first direction will be reflected off the surface of the secondportions. Meanwhile, the interacting surface seen from the seconddirection may appear to consist of both the first and the secondportions. Thus, the radiation incident from the second direction may betransmitted through the first portions of the interacting surface intothe same direction as the reflected radiation from the first direction.

The first portions may be arranged such that the third direction isessentially perpendicular to the mutual direction. Then, the radiationincident from the second direction may incide on the first portions withan angle of incidence of 90°. This implies that essentially all of thisradiation inciding on a first portion will then be transmitted withoutbeing deflected.

According to one embodiment, the optical component reflects the firstelectromagnetic radiation through internal reflection. Then, the secondportions of the interacting surface of the optical component need nothave a surface which is processed for optimal reflection properties.Instead, the total internal reflection which may occur when radiationpasses from a thicker to a thinner medium is used. When the angle ofincidence is larger than a critical angle all radiation incident on thesecond portions is reflected through total internal reflection.

Radiation directed out from the optical component will form a checkedpattern, since the radiation incident on the interacting surface willnot impinge on a continuous surface. According to one embodiment, allfirst portions are of equal size and all second portions are of equalsize. This implies that the radiation directed out from the opticalcomponent will form a uniform pattern.

The first portions and the second portions may be of equal size. Thisimplies that all areas of the checked pattern will be equally large.Further, half of the radiation incident from the second direction willimpinge on a first portion of the interacting surface. Thus, 50% of theradiation incident from the second direction will be transmitted.

According to one embodiment, an angle between the third and the fourthdirections is essentially 45°. This implies that the radiation incidentfrom the first direction, while being parallel to the third direction,in which the surfaces of the first portions extend, will be deflectedthrough reflection into the same direction as the radiation incidentfrom the second direction is transmitted in. Thus, the interactingsurface seen from the first direction will appear to be consisting onlyof the second portions.

The passive optical component may further comprise a plane input surfaceextending in a direction perpendicular to the third direction. Theradiation incident from the first direction may impinge the inputsurface and be transmitted through the optical component to theinteracting surface. When the input surface extends in a directionperpendicular to the third direction, the radiation incident from thefirst direction may impinge perpendicularly to this input surface whilethe first direction is parallel to the third direction. Then, allradiation incident from the first direction will be transmitted throughthe input surface without deflection.

The passive optical component may further comprise a plane outputsurface extending in a direction perpendicular to the mutual direction.This implies that all the radiation propagating in the mutual directionafter having interacted with the interacting surface will leave theoptical component through the output surface without being deflected.

The interacting surface may extend from a first end of the outputsurface to a first end of the input surface. Thus, all radiationincident on the input surface in the first direction will impinge on theinteracting surface and all radiation leaving the interacting surface inthe mutual direction will leave the optical component through the outputsurface.

A second end of the input surface may be connected to a second end ofthe output surface. Thus, the input surface, the interacting surface,and the output surface will form an essentially triangularcross-section. This implies that the optical component will have asimple shape.

The passive optical component may be essentially formed of a plasticmaterial. The optical component may easily be shaped to a desired formin a plastic material. Further, a plastic material having requiredoptical characteristics may easily be found.

According to an aspect of the invention, an optical system is providedfor spectrophotometric analysis. The optical system comprises means forproviding first and second electromagnetic radiation of a first and asecond wavelength, respectively. The optical system further comprises apassive optical component for directing said first and said secondelectromagnetic radiation in a mutual direction. The passive opticalcomponent comprises an interacting surface which is arranged to interactwith said first and second electromagnetic radiation. The interactingsurface comprises first portions, each having a surface extending in afirst direction, which is essentially perpendicular to the mutualdirection, and second portions, each having a surface extending in asecond direction. Thus, the passive optical component reflectsessentially all of said first electromagnetic radiation and transmits atleast a significant portion of the second electromagnetic radiation fordirecting the first and the second electromagnetic radiation in themutual direction.

According to another aspect of the invention, a method is provided forspectrophotometric analysis of a sample. The method comprises the stepsof emitting first electromagnetic radiation of a first wavelength andsecond electromagnetic radiation of a second wavelength, directing thefirst electromagnetic radiation and the second electromagnetic radiationto a mutual direction by means of a passive optical component. Thepassive optical component comprises an interacting surface which isarranged to interact with said first and second electromagneticradiation. The interacting surface comprises first portions, each havinga surface extending in a first direction, which is essentiallyperpendicular to the mutual direction, and second portions, each havinga surface extending in a second direction. Thus, the passive opticalcomponent reflects essentially all of said first electromagneticradiation and transmits at least a significant portion of said secondelectromagnetic radiation for directing the first and the secondelectromagnetic radiation to the mutual direction. The method furthercomprises the step of detecting electromagnetic radiation propagating inthe mutual direction after it has been transmitted through the sample.

A spectrophotometric analysis using this optical system or by means ofthis method may utilize a large portion of the emitted electromagneticradiation without the need for any moveable parts or any change in theoptical setup during the analysis. This implies that the system is veryeasy to use and robust. Thus, it is suited for domestic use.

The system and the method take advantage of the excellent opticalcharacteristics of the passive optical component. The optical system maybe used for irradiating a sample with the first and the secondelectromagnetic radiation simultaneously or separately.

According to one embodiment, the means for providing first and secondelectromagnetic radiation comprises a first and a second source, whichemit the first and second electromagnetic radiation, respectively. Thisimplies that sources which are designed for emitting only thewavelengths that are needed for the spectrophotometric analysis may beused. Thus, the radiation emitted by the sources may be usedeffeciently.

According to another embodiment, the means for providing first andsecond electromagnetic radiation comprises a source, which emits boththe first and the second electromagnetic radiation.

The means for providing first and second electromagnetic radiation mayfurther comprise means for splitting the electromagnetic radiation ofthe source into a first and a second path and filters for transmittingthe first electromagnetic radiation of the first path and the secondelectromagnetic radiation of the second path. Hereby, the radiation ofthe first and the second wavelengths may be extracted from the radiationemitted by the source and may be directed in different directionstowards the passive optical component.

The optical system may further comprise a diffusor for smoothing out theradiation intensity over a cross-section of the electromagneticradiation propagating in the mutual direction. The electromagneticradiation that leaves the passive optical component propagating in themutual direction may not have a homogenous radiation intensity over itscross-section. It may be therefore be suitable to lead the radiationthrough a diffusor.

The method for spectrophotometric analysis may be used for determiningan amount of a chemical substance in a body fluid. The chemicalsubstance may typically be any one of glucose, hemoglobin, albumin,creatinine, cholesterol, HDL-cholesterol, triglycerides, or CRP.Further, the body fluid may be any one of blood, plasma, serum, andurine. Thus, the method may e.g. be used for determining glucose in ablood sample. The method for spectrophotometric analysis is so simplethat it is suitable for domestic use. Thus, it may provide a fastmethod, which a diabetic may use for determining the glucose content inhis/her blood.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described in more detail by way ofexample referring to the appended drawings.

FIG. 1 is a perspective view of an optical component according to theinvention.

FIG. 2 is a side view of the optical component of FIG. 1 illustratingthe path for radiation from a first direction.

FIG. 3 is a side view of the optical component of FIG. 1 illustratingthe path for radiation from a second direction.

FIG. 4 is a schematic view of an optical system according to theinvention.

FIG. 5 is a flow chart illustrating a method according to the invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

Referring to FIG. 1, an optical component 2 according to the inventionwill be described. The optical component 2 comprises an interactingsurface 4, which is intended to interact with electromagnetic radiationimpinging on the optical component 2. The interacting surface 4 isformed according to a repetitive pattern. The interacting surface 4comprises first portions 6 having a surface extending in a firstdirection and second portions 8 having a surface-extending in a seconddirection. The interacting surface 4 is constituted of alternating firstportions 6 and second portions 8. The first and the second directionsform an angle of 45°.

These portions 6, 8 form a “stair-like” shape of the interacting surface4. Several “stair-like” parts are formed side by side in the interactingsurface 4. Two adjacent “stair-like” parts are displaced in depth toeach other. Thus, third portions 10 are formed between the “stair-like”parts. These third portions 10 have a surface, which is perpendicular toboth the surface of the first portions 6 and the surface of the secondportions 8.

As is best seen in FIGS. 2 and 3, the optical component 2 furthercomprises an input surface 12. This input surface 12 is perpendicular tothe first portions 6. The optical component 2 also comprises an outputsurface 14, which is parallel to the first portions 6. The interactingsurface 4 extends from a first end 16, in which it is connected to afirst end 18 of the output surface 14, to a second end 20, in which itis connected to a first end 22 of the input surface 12. The inputsurface 12 is connected in a second end 24 to a second end 26 of theoutput surface 14. The input surface 12 and the output surface 14 form aright angle at their connection. A cross-section of the input surface12, the output surface 14, and the interacting surface 4 form anessentially right angle triangle.

The optical component 4 may be formed in one piece. It is formed of amaterial that has optical characteristics, which are suitable for theelectromagnetic radiation that it is to interact with. The opticalcomponent 4 may be formed of a plastic material that has the requiredoptical characteristics. However, the optical component 4 may also beformed of glass.

Referring now to FIG. 2, the interaction of the optical component 2 withfirst electromagnetic radiation incident from a third direction will beexplained. The first electromagnetic radiation impinges perpendicularlyon the input surface 12 of the optical component 2. The perpendicularincidence implies that essentially all radiation will be transmittedthrough the input surface 12 without being deflected. The firstelectromagnetic radiation propagates in a third direction, which isparallel to the first direction. Thus, the first electromagneticradiation will not impinge on the first portions 6 of the interactingsurface 4. All the first electromagnetic radiation propagating throughthe optical component 2 will interact with the second portions 8 of theoptical component 2. Since these second portions 8 are angled 45′ to thefirst portions 6 and thus to the propagating direction of the firstelectromagnetic radiation, the first electromagnetic radiation will bedeflected 90° by reflection at the second portions. The material of theoptical component 2 has a refractive index that is large enough to causetotal internal reflection for the first electromagnetic radiationimpinging on the second portions 8.

Referring to FIG. 3, the interaction of the optical component 2 withsecond electromagnetic radiation incident from a fourth direction willbe explained. The second electromagnetic radiation is incident on theinteracting surface 4 of the optical component 2. The secondelectromagnetic radiation impinges perpendicularly on the first portions6 of the interacting surface 4. The perpendicular incidence implies thatessentially all radiation will be transmitted through the first portions6 without being deflected. Part of the second electromagnetic radiationwill impinge on the second portions 8 of the interacting surface. Thispart of the second electromagnetic radiation will be reflected or bedeflectedly transmitted. However, the part of the second electromagneticradiation which impinges on the first portions 6 will propagate afterbeing transmitted through the surface in the same directin as the firstelectromagnetic radiation has after it has interacted with the secondportions 8. Thus, the passive optical-component provides a possibilityof directing first electromagnetic radiation incident on the componentin a first direction and second electromagnetic radiation incident onthe component in a second direction to a mutual direction. The opticalcomponent 2 directs essentially all the first electromagnetic radiationto the mutual direction. Only the part of the second electromagneticradiation that is incident on the first portions 6 is directed in themutual direction. Thus, if the first portions 6 and the second portions8 are equally large, 50% of the second electromagnetic radiation will bedirected in the mutual direction.

Both the first and the second electromagnetic radiation directed in themutual direction will form a checkered pattern in their cross-section,the pattern corresponding to the first 6 and second portions 8. Sinceneither the first nor the second electromagnetic radiation is incidenton a continuous surface, the radiation outputted from the interactingsurface 4 will not be continuous over its cross-section. Thus, thecross-section of the first electromagnetic radiation will vary between ahigh intensity in areas corresponding to the interaction with the secondportions 8 and no intensity at all in areas corresponding to theinteraction with the first portions 6, and vice versa for the secondelectromagnetic radiation. The pattern of the cross-section is dependenton the design of the first 6 and the second portions 8.

Referring now to FIG. 4, an optical system 30 using the opticalcomponent 2 will be explained. The optical system 30 comprises a firstand a second electromagnetic radiation sources 32, 34, in the form oflight emitting diodes (LEDs) emitting electromagnetic radiation of twodifferent wavelengths. The first electromagnetic radiation source 32emits first electromagnetic radiation of a first wavelength. The firstelectromagnetic radiation passes a collimator 36 and is then incident onthe interactive surface 4. The second electromagnetic source 34 emitssecond electromagnetic radiation of a second wavelength. The secondelectromagnetic radiation passes a collimator 40 and is then reflectedby a reflective surface 42 towards the interactive surface 4 of theoptical component 2.

The first electromagnetic radiation will interact with the opticalcomponent 2 according to the interaction described above with referenceto FIG. 2. The interacting surface 4 of the optical component 2 is incontact with air so that the first electromagnetic radiation will betotally reflected in the second portions of the interacting surface 4.The second electromagnetic radiation will interact with the opticalcomponent according to the interaction described above with reference toFIG. 3. Thus, the first and the second electromagnetic radiation aredirected into a mutual direction. The first and second electromagneticradiation outputted from the optical component are then reflected in areflective surface 44 towards a sample. The first and the secondelectromagnetic radiation irradiate the same portion of the sample 46.

The optical system 30 further comprises a detector 48. The detector 48detects radiation that has been transmitted through the sample 46. Sincethe first and the second electromagnetic radiation propagate in a mutualdirection, they will interact with the same parts of the sample 46. Thedetected radiation is then analyzed, whereby an amount of a constituentin the sample 46 may be determined.

The optical system 30 may comprise a diffusor (not shown) arranged inthe radiation path after the optical component 2. The diffusor willsmooth out the intensity distribution of the electromagnetic radiation.Thus, the checkered pattern of the electromagnetic radiation will bediffused into a more continuous pattern. The smooth distribution of theintensity of the electromagnetic radiation will provide a more uniforminteraction between the electromagnetic radiation and the sample 48 overthe cross-section of the radiation.

A larger portion of the first electromagnetic radiation than of thesecond electromagnetic radiation is directed into the mutual directionby the optical component 2. The second source 34 emitting the secondelectromagnetic radiation may be stronger than the first source 32 tocompensate for this. However, it may be desired that the radiation ofthe first wavelength has a larger intensity than the radiation of thesecond wavelength, e.g. if the radiation of the second wavelength isused for the purpose of calibration.

Referring to FIG. 5, a method for spectrophotometric analysis of asample 48 will now be described. First, a sample 48 that is to beanalyzed is obtained, step 102, and prepared to suit the analysis. Thesample is analyzed using the optical system 30 described above.

Thus, first electromagnetic radiation of a first wavelength and secondelectromagnetic radiation of a second wavelength are emitted, step 104.The first electromagnetic radiation and the second electromagneticradiation are directed to a mutual direction by means of the passiveoptical component, step 106. The first and the second electromagneticradiation are then passed through the sample 48, step 108.

Next, the electromagnetic radiation that has been transmitted throughthe sample 48 is detected, step 110. Then, the detected amounts ofradiation is analyzed and an amount of a constituent in the sample 48 isdetermined, step 112.

The sample 48 may e.g. be a blood sample. Thus, the determined amountmay be an amount of the glucose in the blood. The optical system 30 maybe so simply designed that a diabetic may use it at home for determininghis or her glucose value.

Of course, other measurements are possible. The spectrophotometricanalysis may be used for determining an amount of any substancesuspended in a liquid.

It should be emphasized that the preferred embodiment described hereinis in no way limiting and that many alternative embodiments are possiblewithin the scope of protection defined by the appended claims. Forexample, the pattern formed by the first and the second portions may bevaried in infinite ways. If the first portions are made larger than thesecond portions, a larger part of the second electromagnetic radiationwill be transmitted through the interacting surface. Further, the anglebetween the first and the second portions may be varied. In this case,the angle of incidence of the first electromagnetic radiation will alsohave to be changed, so that the first electromagnetic radiation isreflected into the mutual direction. However, this implies that thefirst electromagnetic radiation will not propagate in parallel with thefirst portions. Thus, a small part of the first electromagneticradiation will be lost through interaction with the first portions.

The optical system may be arranged such that the electromagneticradiation of the two sources is emitted at the same time orsequentially. The sources need not emit a specific, discrete wavelength,instead they may emit wavelengths of different intervals. Further, onlyone source may be used. In this case, the electromagnetic radiation isdivided into two paths. In a first path, a first wavelength is passed,and in a second path a second wavelength is passed. The electromagneticradiation of the first path and of the second path are then fed to theoptical component in a similar way as the first and secondelectromagnetic radiation described above.

1. A passive optical component for directing first electromagneticradiation incident on the component in a first direction and secondelectromagnetic radiation incident on the component in a seconddirection to a mutual direction, wherein: an interacting surface whichis arranged to interact with said first and second electromagneticradiation, said interacting surface comprising first portions, eachhaving a surface extending in a third direction, which is essentiallyperpendicular to the mutual direction, and second portions, each havinga surface extending in a fourth direction, whereby the optical componentreflects essentially all the first electromagnetic radiation and theoptical component transmits at least a significant portion of the secondelectromagnetic radiation for directing the first and the secondelectromagnetic radiation to a mutual direction.
 2. The passive opticalcomponent according to claim 1, wherein the optical component reflectsthe first electromagnetic radiation through internal reflection.
 3. Thepassive optical component according to claim 1, wherein all firstportions are of equal size and all second portions are of equal size. 4.The passive optical component according to claim 1, wherein the firstportions and the second portions are of equal size.
 5. The passiveoptical component according to claim 4, wherein an angle between thethird and the fourth directions is essentially 45°.
 6. The passiveoptical component according to claim 1, further comprising a plane inputsurface extending in a direction perpendicular to the third direction.7. The passive optical component according to claim 6, furthercomprising a plane output surface extending in a direction perpendicularto the mutual direction.
 8. The passive optical component according toclaim 7, wherein the interacting surface extends from a first end of theoutput surface to a first end of the input surface.
 9. The passiveoptical component according to claim 8, wherein a second end of theinput surface is connected to a second end of the output surface. 10.The passive optical component according to claim 1, said component beingessentially formed of a plastic material.
 11. An optical system forspectrophotometric analysis comprising means for providing first andsecond electromagnetic radiation of a first and a second wavelength,respectively, wherein: a passive optical component for directing saidfirst and said second electromagnetic radiation in a mutual direction,said passive optical component comprising an interacting surface whichis arranged to interact with said first and second electromagneticradiation, said interacting surface comprising first portions, eachhaving a surface extending in a first direction, which is essentiallyperpendicular to the mutual direction, and second portions, each havinga surface extending in a second direction, whereby the optical componentreflects essentially all of said first electromagnetic radiation andtransmits at least a significant portion of the second electromagneticradiation for directing the first and the second electromagneticradiation in the mutual direction.
 12. The optical system according toclaim 11, wherein the means for providing first and secondelectromagnetic radiation comprises a first and a second source, whichemit the first and second electromagnetic radiation, respectively. 13.The optical system according to claim 11, wherein the means forproviding first and second electromagnetic radiation comprises a source,which emits both the first and the second electromagnetic radiation. 14.The optical system according to claim 13, wherein the means forproviding first and second electromagnetic radiation further comprisesmeans for splitting the electromagnetic radiation of the source into afirst and a second path and filters for transmitting the firstelectromagnetic radiation of the first path and the secondelectromagnetic radiation of the second path.
 15. The optical systemaccording to claim 11, further comprising a diffusor for smoothing outthe radiation intensity over a cross-section of the electromagneticradiation propagating in the mutual direction.
 16. A method forspectrophotometric analysis of a sample, said method comprising thesteps of: emitting first electromagnetic radiation of a first wavelengthand second electromagnetic radiation of a second wavelength, directingthe first electromagnetic radiation and the second electromagneticradiation to a mutual direction by means of a passive optical component,said passive optical component comprising an interacting surface whichis arranged to interact with said first and second electromagneticradiation, said interacting surface comprising first portions, eachhaving a surface extending in a first direction, which is essentiallyperpendicular to the mutual direction, and second portions, each havinga surface extending in a second direction, whereby the optical componentreflects essentially all of said first electromagnetic radiation andtransmits at least a significant portion of said second electromagneticradiation for directing the first and the second electromagneticradiation to the mutual direction, and detecting electromagneticradiation propagating in the mutual direction after it has beentransmitted through the sample.
 17. The method according to claim 16 fordetermining an amount of a chemical substance in a body fluid.
 18. Themethod according to claim 17, wherein the chemical substance is one inthe group of glucose, hemoglobin, albumin, creatinine, cholesterol,HDL-cholesterol, triglycerides, and CRP.
 19. The method according toclaim 16, wherein the body fluid is one in the group of blood, plasma,serum, and urine.
 20. The passive optical component according to claim2, wherein all first portions are of equal size and all second portionsare of equal size.
 21. The passive optical component according to claim2, wherein the first portions and the second portions are of equal size.22. The passive optical component according to claim 3, wherein thefirst portions and the second portions are of equal size.
 23. Thepassive optical component according to claim 20, wherein the firstportions and the second portions are of equal size.
 24. The opticalsystem according to claim 12, further comprising a diffusor forsmoothing out the radiation intensity over a cross-section of theelectromagnetic radiation propagating in the mutual direction.
 25. Theoptical system according to claim 13, further comprising a diffusor forsmoothing out the radiation intensity over a cross-section of theelectromagnetic radiation propagating in the mutual direction.
 26. Theoptical system according to claim 14, further comprising a diffusor forsmoothing out the radiation intensity over a cross-section of theelectromagnetic radiation propagating in the mutual direction.
 27. Themethod according to claim 17, wherein the body fluid is one in the groupof blood, plasma, serum, and urine.